Flame-retardant fabric and protective clothing made of the same

ABSTRACT

The present invention relates to a flame-retardant fabric that includes modacrylic fibers, one or more of regenerated cellulose fibers selected from the group consisting of flame-retardant rayon fibers and lyocell fibers, and polyimide fibers. The flame-retardant fabric includes the modacrylic fibers in an amount of 26 to 79 wt%, the regenerated cellulose fibers in an amount of 18 to 48 wt%, and the polyimide fibers in an amount of 3 to 26 wt%. The polyimide fibers have a fiber length of 45 to 127 mm. The char length measured by a flammability test based on GB/T 5455-1997 is 50 mm or less. The present invention also relates to protective clothing made of the flame-retardant fabric. Thus, the present invention provides a flame-retardant fabric whose char length is short in a flammability test and that has favorable flame retardancy, and protective clothing made of the flame-retardant fabric.

TECHNICAL FIELD

The present invention relates to a flame-retardant fabric and protective clothing made of the flame-retardant fabric.

BACKGROUND ART

Accidents such as a fire may happen in workplaces in the fields of petroleum, petrochemistry, coal mine, electric power, welding, and the like. Also, accidents such as a dust explosion may happen in workplaces in the fields of metalworking and the like. Accordingly, protective clothing to be worn in such workplaces is required to have flame retardancy.

Fabrics with various configurations have been proposed as fabrics for flame-retardant protective clothing. For example, Patent Document 1 discloses a fabric that is mainly made of aramid fibers such as para-aramid fibers or meta-aramid fibers. However, aramid fibers are expensive, which causes a bottleneck in widespread use of safe products. Meanwhile, Patent Document 2 discloses a flame-retardant fabric that includes modacrylic fibers, cellulose fibers, and polyimide fibers.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP 2014-525520A -   Patent Document 2: CN 105926097 A

DISCLOSURE OF INVENTION Problem to Be Solved by the Invention

However, when a flammability test is performed on the flame-retardant fabric disclosed in Patent Document 2, its char length may increase. Accordingly, further improved flame retardancy is required.

The present invention provides a flame-retardant fabric whose char length is short in a flammability test and that has favorable flame retardancy, and protective clothing made of the flame-retardant fabric.

Means for Solving Problem

The present invention relates to a flame-retardant fabric that includes modacrylic fibers, one or more of regenerated cellulose fibers selected from the group consisting of flame-retardant rayon fibers and lyocell fibers, and polyimide fibers, wherein the flame-retardant fabric includes the modacrylic fibers in an amount of 26 to 79 wt%, the regenerated cellulose fibers in an amount of 18 to 48 wt%, and the polyimide fibers in an amount of 3 to 26 wt%, the polyimide fibers have a fiber length of 45 to 127 mm, and a char length flame-retardant fabric measured by a flammability test based on GB/T 5455-1997 is 50 mm or less.

The present invention also relates to protective clothing made of the flame-retardant fabric.

EFFECTS OF THE INVENTION

The present invention can provide a flame-retardant fabric whose char length is short in a flammability test and that has favorable flame retardancy, and protective clothing made of the flame-retardant fabric.

DESCRIPTION OF INVENTION

The inventors of the present invention conducted numerous studies in order to improve the flame retardancy of a flame-retardant fabric that includes modacrylic fibers, cellulose fibers, and polyimide fibers. As a result, they surprisingly found that, when a flammability test was performed on a fabric made of predetermined amounts of modacrylic fibers, flame-retardant rayon fibers and/or lyocell fibers, and polyimide fibers in which the polyimide fibers had a fiber length of 45 to 127 mm, the char length of the fabric was short, specifically 50 mm or less. In particular, they found that, when the polyimide fibers had a fiber length of 45 mm or more, the char length of the fabric was short, specifically 50 mm or less, in a flammability test even in the case where the content of polyimide was small. In the present invention, the “char length” can be measured by a flammability test based on GB/T 5455-1997. Note that “GB” as used herein means the “Chinese National Standard”.

Specifically, the inventors of the present invention found that, when a flame-retardant fabric was made of spun yarn that includes modacrylic fibers, flame-retardant rayon fibers and/or lyocell fibers, and polyimide fibers, and the blend amounts of the fibers in this flame-retardant fabric were the same, the char length was significantly short in a flammability test and the flame retardancy was significantly improved in the case where the polyimide fibers had a fiber length of 45 to 127 mm. Conventionally, the type, the blend amount, and the like of fibers used to impart flame retardancy to a fabric are mainly adjusted in order to improve the flame retardancy of a flame-retardant fabric. The finding that the fiber length of fibers has an influence on flame retardancy leads to a breakthrough. The means for improving flame retardancy of a fabric, particularly a fabric made of spun yarn, by setting the fiber length of polyimide fibers in a predetermined range, and thereby significantly reducing the char length of the fabric in a flammability test is innovative, and a person skilled in the art cannot easily devise it.

The flame-retardant fabric includes modacrylic fibers in an amount of 26 to 79 wt%, regenerated cellulose fibers selected from the group consisting of flame-retardant rayon fibers and lyocell fibers in an amount of 18 to 48 wt%, and polyimide fibers in an amount of 3 to 26 wt%. From the viewpoint of the cost and the flame retardancy, it is preferable that the flame-retardant fabric includes modacrylic fibers in an amount of 44.5 to 79 wt%, regenerated cellulose fibers selected from the group consisting of flame-retardant rayon fibers and lyocell fibers in an amount of 18 to 48 wt%, and polyimide fibers in an amount of 3 to 7.5 wt%.

Specifically, the flame-retardant fabric can be made of spun yarn that includes modacrylic fibers in an amount of 26 to 79 wt%, regenerated cellulose fibers selected from the group consisting of flame-retardant rayon fibers and lyocell fibers in an amount of 18 to 48 wt%, and polyimide fibers in an amount of 3 to 26 wt%. From the viewpoint of the cost and the flame retardancy, it is preferable that the flame-retardant fabric is made of spun yarn that includes modacrylic fibers in an amount of 44.5 to 79 wt%, regenerated cellulose fibers selected from the group consisting of flame-retardant rayon fibers and lyocell fibers in an amount of 18 to 48 wt%, and polyimide fibers in an amount of 3 to 7.5 wt%. The spun yarn can be manufactured using a known spinning method. Examples of the spinning method include ring spinning, air spinning, and air-jet spinning, but there is no particular limitation thereto.

The polyimide fibers have a fiber length of 45 to 127 mm. When the polyimide fibers have a fiber length of 45 mm or more, it is possible to improve the flame retardancy and significantly reduce the char length of the fabric in a flammability test. When the polyimide fibers have a fiber length of 127 mm or less, the spun yarn can be produced using a general-purpose spinning apparatus, which leads to favorable productivity. From the viewpoint of the flame retardancy and the productivity in the spinning process, the polyimide fibers preferably have a fiber length of 45 to 76 mm, more preferably 45 to 64 mm, and even more preferably 45 to 55 mm.

There is no particular limitation on the polyimide fibers, and polyimide fibers made of polyimide formed through polymerization of a tetracarboxylic acid component and a diamine component can be used as appropriate, for example.

Examples of the tetracarboxylic acid component include tetracarboxylic dianhydrides. For example, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), oxydiphthalic anhydride (ODPA), and the like can be favorably used as the tetracarboxylic dianhydride, but there is no particular limitation thereto. The tetracarboxylic dianhydrides may be used alone or in combination of two or more.

Examples of the diamine component include diisocyanate compounds and diamine compounds. For example, 2,4-toluene diisocyanate, 2,5-toluene diisocyanate, 2,6-toluene diisocyanate, and the like can be favorably used as the diisocyanate compound, but there is no particular limitation thereto. The diamine compound is preferably an aromatic diamine compound. For example, paraphenylene diamine (PPD), 2,2′-dimethyl-4,4′-diaminobiphenyl(m-tolidine), 4,4′-diaminodiphenyl ether (ODA), 3,4′-diaminodiphenyl ether, 2,2′-bis(trifluoromethyl)benzidine, and the like can be favorably used as the aromatic diamine compound, but there is no particular limitation thereto. The diamine components may be used alone or in combination of two or more.

From the viewpoint of the flame retardancy and the cost, for example, the flame-retardant fabric preferably includes polyimide fibers in an amount of 3 to 7.5 wt%, more preferably in an amount of 4 to 7 wt%, even more preferably in an amount of 4.5 to 6.5 wt%, and particularly preferably in an amount of 5 to 6.5 wt%, but there is no particular limitation thereto.

A commercially available product such as ASPI (registered trademark) polyimide fibers manufactured by China Jiangsu Aoshen Hi-Tech Materials Co., Ltd may also be used as the polyimide fibers.

The modacrylic fibers are preferably made of an acrylonitrile copolymer formed through copolymerization of 35 to 85 wt% of acrylonitrile and 15 to 65 wt% of another component. From the viewpoint of the flame retardancy, it is preferable to use, as the other component, one or more components selected from, for example, the group consisting of halogen-containing vinyl monomers and halogen-containing vinylidene monomers. The content of acrylonitrile in the acrylonitrile copolymer is more preferably 35 to 65 wt%. The contents of a halogen-containing vinyl monomer and/or a halogen-containing vinylidene monomer in the acrylonitrile copolymer are more preferably 35 to 65 wt%. The acrylonitrile copolymer may further include a monomer having a sulfonic group. The content of a monomer having a sulfonic group in the acrylonitrile copolymer is preferably 0 to 3 wt%.

The acrylonitrile copolymer preferably includes acrylonitrile in an amount of 35 to 85 wt%, one or more halogen-containing monomers selected from the group consisting of halogen-containing vinyl monomers and halogen-containing vinylidene monomers in an amount of 15 to 65 wt%, and a monomer having a sulfonic group in an amount of 0 to 3 wt%, and more preferably includes acrylonitrile in an amount of 40 to 75 wt%, one or more halogen-containing monomers selected from the group consisting of halogen-containing vinyl monomers and halogen-containing vinylidene monomers in an amount of 24.5 to 60 wt%, and a monomer having a sulfonic group in an amount of 0.5 to 3 wt%.

When the content of acrylonitrile in the acrylonitrile copolymer is 35 to 85 wt%, the modacrylic fibers have favorable fiber physical properties, and thus the flame-retardant fabric that includes the modacrylic fibers also have favorable physical properties.

When the contents of the halogen-containing vinyl monomer and/or the halogen-containing vinylidene monomer in the acrylonitrile copolymer are 15 to 65 wt%, the modacrylic fibers have favorable flame retardancy, and thus the flame-retardant fabric that includes the modacrylic fibers also have favorable flame retardancy.

Examples of the halogen-containing vinyl monomers include vinyl chloride and vinyl bromide, but there is no particular limitation thereto. Examples of the halogen-containing vinylidene monomers include vinylidene chloride and vinylidene bromide, but there is no particular limitation thereto. The halogen-containing vinyl monomers and the halogen-containing vinylidene monomers may be used alone or in combination of two or more.

Examples of the monomer having a sulfonic group include methacrylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, and salts thereof, but there is no particular limitation thereto. Examples of the salts include sodium salts, potassium salts, and ammonium salts, but there is no limitation thereto. The monomers having a sulfonic group may be used alone or in combination of two or more. The monomer having a sulfonic group is used as necessary, but when the content of the monomer having a sulfonic group in the acrylonitrile copolymer is 3 wt% or less, the production stability in the spinning process will be excellent.

It is preferable that the modacrylic fibers contain an antimony compound. The content of the antimony compound in each of the modacrylic fibers is 3.9 to 20 wt%, preferably 4.2 to 18 wt%, more preferably 4.5 to 16 wt%, and even more preferably 4.7 to 14 wt%, with respect to the overall weight of the fiber. When the content of the antimony compound is within the above-described range, the char length is more likely to decrease in a flammability test, and the afterglow time also decreases.

From the viewpoint of the production stability in the spinning process, the antimony compound is preferably one or more compounds selected from the group consisting of antimony trioxide, antimony tetroxide, and antimony pentoxide, but there is no particular limitation thereto.

From the viewpoint of the strength and the productivity in the spinning process, for example, short fibers having a fiber length of 30 to 127 mm, preferably 45 to 127 mm, more preferably 45 to 76 mm, and even more preferably 45 to 64 mm, can be appropriately used as the modacrylic fibers. It is preferable that the modacrylic fibers have substantially the same fiber length as that of the polyimide fibers. This makes it possible to improve the spinnability and thereby increase the yarn quality such as strength, and thus the physical properties of the flame-retardant fabric may be improved.

From the viewpoint of the flame retardancy and the thermal resistance, the flame-retardant fabric preferably includes modacrylic fibers in an amount of 44.5 to 65 wt%, more preferably in an amount of 50 to 65 wt%, and even more preferably in an amount of 50 to 60 wt%.

It is preferable that rayon fibers containing a phosphorus-based flame retardant are used as the flame-retardant rayon fibers. Examples of the phosphorus-based flame retardant include phosphoric ester-based compounds, halogen-containing phosphoric ester-based compounds, condensed phosphoric ester-based compounds, polyphosphate-based compounds, and polyphosphoric ester-based compounds, but there is no particular limitation thereto. The flame-retardant rayon fibers containing the phosphorus-based flame retardant preferably include, for example, the phosphorus-based flame retardant in an amount of 0.5 wt% or more, and more preferably 0.8 wt% or more, with respect to the overall weight of the fibers, but there is no particular limitation thereto. For example, commercially available flame-retardant rayon fibers such as flame-retardant rayon “Lenzing FR (registered trademark)” manufactured by Lenzing and flame-retardant rayon “JWELL FR (trademark)” manufactured by Jilin Chemical Fibre Co., Ltd. may also be used as the flame-retardant rayon fibers containing the phosphorus-based flame retardant.

The flame-retardant fabric includes phosphorus in an amount of 0.3 wt% or more, preferably 0.4 wt% or more, and more preferably 0.5 wt% or more, with respect to the overall weight of the fabric. When the content of phosphorus in the flame-retardant fabric is 0.3 wt% or more, the char length is more likely to decrease, and the flame retardancy is further improved. Note that, although there is no particular limitation on the upper limit of the content of phosphorus in the flame-retardant fabric, the content of phosphorus is preferably 1.1 wt% or less with respect to the overall weight of the fabric from the viewpoint of further reducing the char length of the flame-retardant fabric. The content of phosphorus in the flame-retardant fabric can be measured using a fluorescent X-ray analysis method.

When the flame-retardant fabric includes the modacrylic fibers made of an acrylonitrile copolymer formed through copolymerization of acrylonitrile and a vinyl halide monomer, the flame-retardant fabric preferably includes flame-retardant rayon fibers as the regenerated cellulose fibers from the viewpoint of further improving the flame retardancy.

Due to the regenerated cellulose fibers includedin the flame-retardant fabric in addition to the polyimide fibers and modacrylic fibers, an excellent texture and moisture absorbency can be imparted to the flame-retardant fabric while the flame retardancy is improved.

From the viewpoint of the flame retardancy and the texture, the flame-retardant fabric preferably includes the regenerated cellulose fibers in an amount of 18 to 45 wt%, and more preferably in an amount of 20 to 40 wt%.

From the viewpoint of the strength and the productivity in the spinning process, for example, short fibers having a fiber length of 30 to 127 mm, preferably 45 to 127 mm, more preferably 45 to 76 mm, and even more preferably 45 to 64 mm, can be appropriately used as the flame-retardant rayon fibers and the lyocell fibers. It is preferable that the flame-retardant rayon fibers and the lyocell fibers have substantially the same fiber length as that of the polyimide fibers. This makes it possible to improve the spinnability and thereby increase the yarn quality such as strength, and thus the physical properties of the flame-retardant fabric may be improved. It is particularly preferable that the modacrylic fibers, the flame-retardant rayon fibers, and the lyocell fibers have substantially the same fiber length as that of the polyimide fibers.

The flame-retardant fabric may include other fibers as long as the object and the effects of the present invention are not inhibited. Examples of the other fibers include conductive fibers, nylon fibers, and polyester fibers. The flame-retardant fabric may include the other fibers in an amount of 5 wt% or less, 3 wt% or less, or 1 wt% or less.

From the viewpoint of the strength and the productivity in the spinning process, for example, short fibers having a fiber length of 30 to 127 mm can be appropriately used as the other fibers, and the fiber length is preferably 45 to 127 mm, more preferably 45 to 76 mm, and even more preferably 45 to 64 mm, from the viewpoint of the productivity in the spinning process. It is preferable that the other fibers have substantially the same fiber length as that of the polyimide fibers. This makes it possible to improve the spinnability and thereby increase the yarn quality such as strength, and thus the physical properties of the flame-retardant fabric may be improved. It is particularly preferable that all the fibers included in the spun yarn have substantially the same fiber length as that of the polyimide fibers.

From the viewpoint of the strength of the flame-retardant fabric, all of the modacrylic fibers, the flame-retardant rayon fibers, the lyocell fibers, and the other fibers preferably have a single fiber fineness of 1 to 20 dtex, and more preferably 1.5 to 15 dtex.

From the viewpoint of the flexibility and feel, the flame-retardant fabric preferably has a basis weight of 100 to 500 g/m², more preferably 130 to 480 g/m², and even more preferably 150 to 460 g/m².

Examples of the form of the flame-retardant fabric include a woven fabric and a knitted fabric, but there is no particular limitation thereto. A woven fabric is preferable from the viewpoint of the durability and flame retardancy. There is no particular limitation on the weave of the woven fabric. Three foundation weave such as a plain weave, a twill weave, and a sateen weave may be applied, and a patterned woven fabric obtained by using a special loom such as a dobby loom or a Jacquard loom may be used.

The flame-retardant fabric has excellent flame retardancy, and the char length measured by a flammability test based on GB/T 5455-1997 is 50 mm or less. When the char length is 50 mm or less, the class-A standard for the char length of a “flame-retardant protective clothing” specified in GB 8965.1-2009 will be satisfied. It is preferable that the char length of the flame-retardant fabric measured by a flammability test based on GB/T 5455-1997 is 50 mm or less after the flame-retardant fabric is washed 50 times in accordance with GB/T 17596-1998.

Also, the flame-retardant fabric has excellent flame retardancy, and the afterglow time measured by a flammability test based on GB/T 5455-1997 is preferably 2.0 seconds or less. It is more preferable that the afterglow time measured by a flammability test based on GB/T 5455-1997 is 2.0 seconds or less after the flame-retardant fabric is washed 50 times in accordance with GB/T 17596-1998. When the afterglow time is 2.0 seconds or less, the class-A or class-B standard for the afterglow time of a “flame-retardant protective clothing” specifiedin GB 8965.1-2009 will be satisfied. It is more preferable that the flame-retardant fabric has a char length of 50 mm or less and an afterglow time of 2.0 seconds or less, and it is particularly preferable that the flame-retardant fabric has a char length of 50 mm or less and an afterglow time of 2.0 seconds or less after being washed 50 times in accordance with GB/T 17596-1998.

Also, it is preferable that the flame-retardant fabric has excellent flame retardancy, and the afterflame time measured by a flammability test based on GB/T 5455-1997 is 2.0 seconds or less. It is more preferable that the afterflame time measured by a flammability test based on GB/T 5455-1997 is 2.0 seconds or less after the flame-retardant fabric is washed 50 times in accordance with GB/T 17596-1998. When the afterflame time is 2.0 seconds or less, the class-A or class-B standard for the afterflame time of a “flame-retardant protective clothing” specified in GB 8965.1-2009 will be satisfied.

The flame-retardant fabric of the present invention can be favorably used as a fabric for protective clothing required to have flame retardancy, thus making it possible to provide, at low cost, protective clothing that is made of the flame-retardant fabric and has excellent flame retardancy. The protective clothing of the present invention can be manufactured using the flame-retardant fabric through a known sewing method. Since the flame-retardant fabric has excellent flame retardancy, the protective clothing of the present invention also has excellent flame retardancy. Also, since the flame-retardant fabric has excellent flame retardancy even after being washed repeatedly, the protective clothing retains flame retardancy even after being washed repeatedly. The protective clothing of the present invention can be used in any operations in which flame retardancy is required. For example, the protective clothing of the present invention can be used as protective clothing to be worn in workplaces in the fields of petroleum, petrochemistry, coal mine, electric power, welding, and the like in which accidents such as a fire may happen, and protective clothing to be worn in workplaces in the fields of metalworking and the like in which accidents such as a dust explosion are likely to happen.

EXAMPLES

Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the examples.

The following fibers were usedin examples and comparative examples.

Fibers

Modacrylic fibers that were made of an modacrylic copolymer containing acrylonitrile in an amount of 49.5 wt%, vinyl chloride in an amount of 49.5 wt%, and sodium styrenesulfonate in an amount of 1.0 wt%, and that contained antimony trioxide in an amount of 9.1 wt% with respect to the overall weight of the fibers were used as modacrylic fibers I.

-   Modacrylic fibers I: fineness of 1.7 dtex, fiber length of 51 mm -   Flame-retardant rayon fibers: “Lenzing FR” manufactured by Lenzing,     containing a phosphorus-based flame retardant, fineness of 2.2 dtex,     fiber length of 51 mm -   Lyocell fibers: “Tencel (registered trademark)” manufactured by     Lenzing, fineness of 1.3 dtex, fiber length of 51 mm -   Polyimide fibers I: “ASPI (registered trademark)” manufactured by     China Jiangsu Aoshen Hi-Tech Materials Co., Ltd, fineness of 1.67     dtex, fiber length of 51 mm -   Polyimide fibers II: “ASPI (registered trademark)” manufactured by     China Jiangsu Aoshen Hi-Tech Materials Co., Ltd, fineness of 1.67     dtex, fiber length of 38 mm

Examples 1 to 3, Comparative Examples 1 to 3

The above-described modacrylic fibers, flame-retardant rayon fibers, lyocell fibers, and polyimide fibers in the blend amounts shown in Table 1 below were mixed to manufacture spun yarns of cotton count Nos. shown in Table 1 below. These spun yarns were used as warp and weft to produce woven fabrics with 2/1 twill weave using a common manufacturing method. The numbers of picks were as shown in Table 1 below.

The flame retardancy of each of the fabrics obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was measured and evaluated as follows. Table 1 shows the results.

Flame Retardancy

Aflammability test was performed based on GB/T 5455-1997 to measure the char length (the length of a carbonized portion), afterflame time, and afterglow time of the fabric. Note that the fabrics of Examples 1 to 3 and Comparative Examples 1 to 3 were washed 50 times in accordance with GB/T 17596-1998 and were then subjected to the flammability test.

TABLE 1 Fiber type: Fiber length (mm) Ex. 1 Ex. 2 Ex. 3 Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Blend amount (wt%) Modacrylic fiber I: 51 55 55 57 55 55 57 Lyocell: 51 17 37 17 17 37 17 Flame retardant rayon: 51 20 0 20 20 0 20 Polyimide fiber 1: 51 8 8 6 0 0 0 Polyimide fiber II: 38 0 0 0 8 8 6 Spun yarn Cotton count No. 36/2 36/2 36/2 36/2 36/2 36/2 Woven fabric Basis weight (g/m²) 230 180 230 230 180 230 Weave 2/1 twill weave 2/1 twill weave 2/1 twill weave 2/1 twill weave 2/1 twill weave 2/1 twill weave Warp density (yarn/2.54 cm) 90 70 90 90 70 90 Weft density (yarn/2.54 cm) 70 55 70 70 55 70 Flammability test Char length (mm) 22 21 29 96 66 122 Afterflame time 0 0 0 0 0 0 Afterglow time 0 0 0 0 0 0

As is clear from the results shown in Table 1 above, the char lengths of the fabrics of Examples 1 to 3 measured by the flammability test based on GB/T 5455-1997 were 50 mm or less, and these fabrics had excellent flame retardancy. On the other hand, when the fabrics of Comparative Examples 1 to 3 that included the polyimide fibers having a fiber length of less than 45 mm were used, the char lengths thereof measured by the flammability test based on GB/T 5455-1997 exceeded 50 mm, and these fabrics had poor flame retardancy. 

1. A flame-retardant fabric comprising: modacrylic fibers; one or more of regenerated cellulose fibers selected from the group consisting of flame-retardant rayon fibers and lyocell fibers; and polyimide fibers, wherein the flame-retardant fabric comprises the modacrylic fibers in an amount of 44.5 to 79 wt%, the regenerated cellulose fibers in an amount of 18 to 48 wt%, and the polyimide fibers in an amount of 3 to 8 wt%, both the polyimide fibers and the modacrylic fibers have a fiber length of 45 to 127 mm, and a char length of the flame-retardant fabric measured by a flammability test based on GB/T 5455-1997 is 50 mm or less.
 2. (canceled)
 3. The flame-retardant fabric according to claim 1, wherein the one or more of regenerated cellulose fibers have a fiber length of 45 to 127 mm.
 4. The flame-retardant fabric according to any one of claim 1, wherein the modacrylic fibers are comprised of an acrylonitrile copolymer that includes acrylonitrile in an amount of 35 to 85 wt%, one or more halogen-containing monomers selected from the group consisting of halogen-containing vinyl monomers and halogen-containing vinylidene monomers in an amount of 15 to 65 wt%, and a vinyl monomer having a sulfonic group in an amount of 3 wt% or less.
 5. The flame-retardant fabric according to any one of claim 1, wherein the modacrylic fibers comprise an antimony compound in an amount of 3.9 to 20 wt%.
 6. The flame-retardant fabric according to any one of claim 1, wherein the flame-retardant rayon fibers comprise a phosphorus-based flame retardant.
 7. The flame-retardant fabric according to any one of claim 1, comprising: the modacrylic fibers in an amount of 44.5 to 79 wt%; the regenerated cellulose fibers in an amount of 18 to 48 wt%; and the polyimide fibers in an amount of 3 to 7.5 wt%.
 8. The flame-retardant fabric according to any one of claim 1, wherein the acrylonitrile copolymer comprises a halogen-containing vinyl monomer, and the regenerated cellulose fibers comprise flame-retardant rayon fibers.
 9. The flame-retardant fabric according to any one of claim 1, which is a woven fabric.
 10. Protective clothing made of the flame-retardant fabric according to any one of claim
 1. 11. The flame-retardant fabric according to claim 1, wherein the regenerated cellulose fibers comprise the lyocell fibers.
 12. The flame-retardant fabric according to claim 1, wherein all of the modacrylic fibers, the regenerated cellulose fibers, and the polyimide fibers have a fiber length of 45 to 64 mm. 